You have: A+B=60° and cos(A)+cos(B)=1
If you write:
cos(A)+cos(B)=1 as 2cos((A+B)/2).cos((A-B)/2)=1
You can solve this one because you know A+B=60° so (A+B)/2=30°
You have now: 2cos(30°).cos((A-B)/2)=1

Now try to finish it.

Jul 11th 2011, 11:39 AM

waqarhaider

Re: trignometry --problem plz help

from given cosA = cos(60-B) substituting in 2nd and simplifying

we get cos(B-30) = 1/(sqrt3) gives B = 84.73561
now you can find A and required values